Antenna



June 27, 1939. R. VON RADINGER 1mrsmu Filed Feb. 26, 1936 Patented June 27, 1939 UNITED STATES PATENT OFFICE ANTENNA tion cf Germany Application February 26, 1.936, Serial N0. 65,747

In Germany 6 Claims.

The present invention relates to a dire-ctional antenna system, and particularly to a directional system which employs a planar untuned reflector.

5 It is kriown that in antenna systems, reflectors o-f different types are frequently used in shortwave wor k for obtaining concentration 01' beaming of the radiated energy 01 the received energy.

The present invention is especially concerned with planar 01 sheet-type refletztors consisting either of solid sheets, or lattice, or grate-work. Hitherto these reflectors, as a rule were mounted at a distance from the radiator ranging between one-quarter and oneflfth the length of the communication wave (d=A/4= to M5, Where is the wavelength). The depth of the entire antenna assembly, in the direction of the mein vecto1 of the beam or the radiations, Will in such case ii be great, and this is a factor Which has been found t0 be inconvenient especially where the equiprhent must be mounted within a casing, er where it is to be transported. In this last mentioned instance, both the weight and the l! dimensions p1ay an important part.

According to this invention, there is provided a beamantenna system compri.sing one or more individual radiator elements, and a planar or sheet refiector having this outstanding char- 80 acteristic, that the distance between the component radiators and. the reflector sheet is 1ess than one-fifth the length of the cornmunication wave (M5).

One important advantage of the invention lies 35 in the small constructional depth which isespecially desirable in the building of transportable outflts. The invention ofiers, in addition, other advantages Which appear from a reaoling of the following description.

40 In short-wave aeria1s, especially portable equipment, the component radiator elements, for reasons of stability and ruggedness, are mostly made from stout wires or tubes (piping) and these are inter-supported and anchored by rela- 45 tively slender supports engaging at points of minimum alternating currnt potential. If, then, an arrangement or structure of this kind is subjected t0 shocks or percussions in transmitter or receiving work, this is liable t0 greatly 50 impair the quality of the transmission. The

supporting means having a length equal to onequarter wavelength (7\/4) yie1d, e1astically, upon each such shock to a greater extent than, for instance, relatively short and stout supports, so

55 that the distance between the antenna and the March 5, 1935 reflector Will be variecl, though only tc a slight degree. Thesefluctuations in the distance alter the characteristic impedance and, under certain circumstances, also the tuning of the antenna. Inasmuch as the entire radiator or antenna is in comparatively close coupling relationship with the (mostly self-excited) oscillator, in the case of a transmitter or a regenerative receiver, these alterations of the characteristie impedance exercise an effect not only upon the amplitucle, but also upon the frequency of the, saY, transmitted oscillations.

In accordance with the present invention, ways and means are provided to minimize the foregoing disadvantages, mainly by reducing the distance between the individual r adiator and the reflector sheet t0 a value qual t0 an eighth of the length of the communication wave (MB) or, where required, even to one-fifteenth (7\/ 15) er one-twentieth (M20) of the wavelength, while the supports are made as rigid as feasible.

The danger 0f the supports being bent is, of course, far less with short supporting pieces inasmuch as the amount of flexure y, assuming equa1 load P at the ends, equal resistance J and equal material E for the supports grows with the third power of the constructidn length l, as

follows:

The spac'er pieces o1 holding rods may be either made from insulation material as known in the art; or else, bursuant to a disclosureof the applicant, the same cou1d be made of metal, and this results in an extremely stable construction which Will measure up t0 all practical requirements and duties.

The effect of small distance upon the characteristic impedance (radiation resistance) and upon the incoming field intensity observed at a given receiving place shall be explained more fully by reference to the accompanying drawing wherein Figs. 1, 2 and 3 illustrate beam antennas to which the present invention may be applied 130 great advantage, as found from actual practice.

Fig', 1, for example illustrates a three row sheet antenna of the directional ty*pe comprising six dipoles Se each cf one-half (M2) wavelength, mounted in front of a reflecting surface F. The dipoles are secured at point s of minimum alternating voltage by supports St having a length d equal, in accordance w1th known practice, to onequarter (M4) the wavelength on the said reflector surface.

Fig. 2 shows the same beam antenna in side elevat ion. Attention is called to the long cumbersome Supports St which, of course, yield far more easily 130 percussions and shocks.

Fig. 3 shows an arrangement o1 an antenna in accordance With a preferred embodiment f the present invention. The length of the supports St amounts t0 only one-fifteenth of a wavelenglth, indicatecl by d=x/ 15; the entire arrangement is far more compact and thus makes a far more ruggecl impression. I1: should. be notecl from this figure that the refiector F extencls above and below the dipoles.

Reduction of the spacers and the distance d between the antenna sheet and the reflector is Valuable particularly in the construction of the portable outfits. From the standpoint of technical and practical utility of such an arrangement, the following denotes in what way the characteristic impedance of the aerial is altered by a reduction of the distance between antenna and reflector. The radiation impedance of a dipole as a function of the reflector distance varies approximately according 130 this formula:

where R is the radiatlon resistance upon the dipole when placed in f1'ont 0f the reflecting surface, and R0 the radiation resistance of the cllpole in spaca far removed from any refltecting surfaces. The wavelength used in these tests was x=50 centimeters.

Whenever the1eis a practical necessity therefor, it; Will alvvays be.feasible to adjust concliti0ns 120 an optimum value by resistance matching between the wave generator and the radiator, for example, by .means of a transformer or suitably designeddipole transmission lines.

The present.invention lt is to be understood, is no1: lim ited solely 130 the use of fixedly mounte.d beam antenna arrangements since i1; is also possible to builcl demountable or collapsible antnnae inaccordance with the invention. Similarly, the reflector neednot be.made solely of a solid sheet of metal, but may consist instead of crossecl grids or grates.

What is claimed ist 1. A direotive antenna system wherein the ohmic losses are substantially small as compared with the radiation resistance having in combination therewith a reflector located in the rear of the antenna and spaced therefrom a distance less than and substantially of a different order than one-quarter of the length of the comrnunication wave. 2. A directive an-tenna especially adapted for short waves comprising a plurality of dipoles in the same vertical plane a reflector having a surface in a plane parallel 130 the plane of said dipoles and locatecl in the rear of said dipoles, said two planes beim; separated by a distance not greater than one-tenth the 1ength of the communicaden wave.

3. A directive antenna comprising one er more radiator elements, and a reflector located. in the rear o1 said elements with respect to the direction o1 comrnunication, saicl one or more radiator elements belng spaced avvay from said refiector a distance substantially equa1 to one-fifteenth of the length of the communication wave.

4. A directive beam antenna comprising a plurality of radiator elements located substantially in the sarne plane, a planar reflector located in the rear of said elements and being in a plane substantially parallel to bhe plane of said elements, the distance beoween said planes being less than one-eighth the length of the communication wave.

5. A directive beam antanna cornprising a plurality0f parallel horizontal dipoles located in bhe Same plane and. mounted in front ofa plane refiecting surface, each 0f said dipoles being substantlally equal to half the length of the communication wave a support extending from the center of each dipole to said reflecting surface, the length 01 saicl support b-eing less than and substantially of a different order than one-quarter 0f the length of the communication wave.

6.. A directive antenna comprising a dipole-and a refleobing surface located in the rear of said dipole a distance less than and. substantially of a different orcler than one-quarter of the length of the communication wave, said refiector having its surface extending beyond the leng-th-of saicl dipole and above and.below said dipola V RUDOLF von RADINGER. 

